Multilayer piezoelectric substrate device with varying interdigital transducer duty factor for temperature stability

ABSTRACT

An acoustic wave filter includes a substrate and a piezoelectric layer over the substrate. First acoustic wave resonators are disposed over the piezoelectric layer and arranged in series along a first branch, and second acoustic wave resonators are disposed over the piezoelectric layer, arranged in parallel, and connected to the first branch and to ground. The first and second acoustic wave resonators include an interdigital transducer electrode interposed between a pair of reflectors. The interdigital transducer electrode of one or more of the second plurality of acoustic wave resonators has a wider duty factor than the interdigital transducer electrodes of the first plurality of acoustic wave resonators.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR 1.57.

BACKGROUND Technical Field

Embodiments of this disclosure relate to acoustic wave devices, and moreparticularly to multilayer piezoelectric substrate devices with improvedtemperature stability.

Description of Related Technology

An acoustic wave filter can include a plurality of acoustic resonatorsarranged to filter a radio frequency signal. Example acoustic wavefilters include surface acoustic wave (SAW) filters and bulk acousticwave (BAW) filters. A surface acoustic wave resonator of a surfaceacoustic wave filter typically includes an interdigital transducerelectrode on a piezoelectric substrate. A surface acoustic waveresonator is arranged to generate a surface acoustic wave.

Acoustic wave filters can be implemented in radio frequency electronicsystems. For instance, filters in a radio frequency front end of amobile phone can include acoustic wave filters. Ideally, the filtersallow frequencies in a specific frequency band and filter out or rejectfrequencies outside the band, within an operating temperature range.However, existing filters have a temperature coefficient of frequency(TCF) near zero for anti-resonant frequency but resonant TCF that canhave a positive value, which results in an edge of the band having alower slope and degraded attenuation (at low temperature).

SUMMARY OF CERTAIN INVENTIVE ASPECTS

The innovations described in the claims each have several aspects, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of the claims, some prominent features ofthis disclosure will now be briefly described.

In accordance with one aspect of the disclosure, an acoustic filterdevice is provided with improved temperature stability.

In accordance with another aspect of the disclosure, an acoustic filterdevice is provided with improved rejection performance for a wide bandpass filter.

In accordance with one aspect of the disclosure, an acoustic filterdevice (e.g., ladder filter device) is provided having one or moreresonators connected in series (“series resonators”) and one or moreresonators connected in parallel and connected to ground (“parallelresonators” or “shunt resonators”). One or more (e.g., all, fewer thanall) of the shunt resonators are covered by a film or layer of negativetemperature coefficient of frequency (TCF) material and the seriesresonators are uncovered (e.g., not covered by a film or layer ofnegative TCF) to tune the TCF values to improve a lower skirt TCF of thefilter device (e.g., synchronize the TCF of the resonant andanti-resonant frequencies for the series resonators and shuntresonators).

In accordance with one aspect of the disclosure, an acoustic filterdevice (e.g., ladder filter device) is provided having one or moreresonators connected in series (“series resonators”) and one or moreresonators connected in parallel and connected to ground (“parallelresonators” or “shunt resonators”). One or more (e.g., all, fewer thanall) of the series resonators are covered by a film or layer of positivetemperature coefficient of frequency (TCF) material and the shuntresonators are uncovered (e.g., not covered by a film or layer ofpositive TCF) to tune the TCF values to improve a lower skirt TCF of thefilter device (e.g., synchronize the TCF of the resonant andanti-resonant frequencies for the series resonators and shuntresonators).

In accordance with one aspect of the disclosure, an acoustic filterdevice (e.g., ladder filter device) is provided having one or moreresonators connected in series (“series resonators”) and one or moreresonators connected in parallel and connected to ground (“parallelresonators” or “shunt resonators”). One or more (e.g., all, fewer thanall) of the shunt resonators have an interdigital transducer (IDT) witha wider duty factor (DF) than one or more (e.g., all, fewer than all) ofthe series resonators to tune the TCF values to improve a lower skirtTCF of the filter device (e.g., synchronize the TCF of the resonant andanti-resonant frequencies for the series resonators and shuntresonators).

In accordance with one aspect of the disclosure, an acoustic filterdevice (e.g., ladder filter device) is provided having one or moreresonators connected in series (“series resonators”) and one or moreresonators connected in parallel and connected to ground (“parallelresonators” or “shunt resonators”). One or more (e.g., all, fewer thanall) of the series resonators have an interdigital transducer (IDT) witha wider duty factor (DF) than one or more (e.g., all, fewer than all) ofthe shunt resonators to tune the TCF values to improve a lower skirt TCFof the filter device (e.g., synchronize the TCF of the resonant andanti-resonant frequencies for the series resonators and shuntresonators).

In accordance with one aspect of the disclosure, an acoustic filterdevice (e.g., ladder filter device) is provided having one or moreresonators connected in series (“series resonators”) and one or moreresonators connected in parallel and connected to ground (“parallelresonators” or “shunt resonators”). One or more (e.g., all, fewer thanall) of the shunt resonators are covered by a film of negativetemperature coefficient of frequency (TCF) material having a firstthickness and one or more (e.g., all, fewer than all) of the seriesresonators are covered by a film of negative temperature coefficient offrequency (TCF) material of a second thickness, the second thicknessbeing smaller than the first thickness to tune the TCF values to improvea lower skirt TCF of the filter device (e.g., synchronize the TCF of theresonant and anti-resonant frequencies for the series resonators andshunt resonators).

In accordance with one aspect of the disclosure, an acoustic filterdevice (e.g., ladder filter device) is provided having one or moreresonators connected in series (“series resonators”) and one or moreresonators connected in parallel and connected to ground (“parallelresonators” or “shunt resonators”). One or more (e.g., all, fewer thanall) of the shunt resonators are covered by a film of positivetemperature coefficient of frequency (TCF) material having a firstthickness and one or more (e.g., all, fewer than all) of the seriesresonators are covered by a film of positive temperature coefficient offrequency (TCF) material of a second thickness, the second thicknessbeing larger than the first thickness to tune the TCF values to improvea lower skirt TCF of the filter device (e.g., synchronize the TCF of theresonant and anti-resonant frequencies for the series resonators andshunt resonators).

In accordance with one aspect of the disclosure, an acoustic filterdevice (e.g., ladder filter device) is provided having one or moreresonators connected in series (“series resonators”) and one or moreresonators connected in parallel and connected to ground (“parallelresonators” or “shunt resonators”). One or more (e.g., all, fewer thanall) of the shunt resonators are covered by a film of negativetemperature coefficient of frequency (TCF) material having a firstthickness and one or more (e.g., all, fewer than all) of the seriesresonators are covered by a film of negative temperature coefficient offrequency (TCF) material of a second thickness smaller than the firstthickness, and one or more (e.g., all, fewer than all, one, two) of theshunt resonators have an interdigital transducer (IDT) with a wider dutyfactor (DF) than one or more (e.g., all, fewer than all) of the seriesresonators, to thereby tune the TCF values to improve a lower skirt TCFof the filter device (e.g., synchronize the TCF of the resonant andanti-resonant frequencies for the series resonators and shuntresonators).

In accordance with one aspect of the disclosure, an acoustic filterdevice (e.g., ladder filter device) is provided having one or moreresonators connected in series (“series resonators”) and one or moreresonators connected in parallel and connected to ground (“parallelresonators” or “shunt resonators”). One or more (e.g., all, fewer thanall) of the shunt resonators are covered by a film of positivetemperature coefficient of frequency (TCF) material having a firstthickness and one or more (e.g., all, fewer than all) of the seriesresonators are covered by a film of positive temperature coefficient offrequency (TCF) material of a second thickness larger than the firstthickness, and one or more (e.g., all, fewer than all, one, two) of theseries resonators have an interdigital transducer (IDT) with a widerduty factor (DF) than one or more (e.g., all, fewer than all) of theshunt resonators, to thereby tune the TCF values to improve a lowerskirt TCF of the filter device (e.g., synchronize the TCF of theresonant and anti-resonant frequencies for the series resonators andshunt resonators).

In accordance with one aspect of the disclosure, an acoustic wave filteris provided. The acoustic waive filter comprises a substrate and apiezoelectric layer disposed over the substrate. A first plurality ofacoustic wave resonators is disposed over the piezoelectric layer andarranged in series along a first branch, each of the first plurality ofacoustic wave resonators comprising an interdigital transducer electrodeinterposed between a pair of reflectors. A second plurality of acousticwave resonators is disposed over the piezoelectric layer and arranged inparallel, each of the second plurality of acoustic wave resonatorscomprising an interdigital transducer electrode interposed between apair of reflectors and being connected to the first branch and toground. A layer of negative temperature coefficient of frequencydielectric material is disposed over one or more of the second pluralityof acoustic wave resonators.

In accordance with another aspect of the disclosure, a radio frequencymodule is provided. The radio frequency module comprises a packagesubstrate and an acoustic wave filter configured to filter a radiofrequency signal. The acoustic wave filter includes a substrate, and apiezoelectric layer over the substrate. A first plurality of acousticwave resonators is disposed over the piezoelectric layer and arranged inseries along a first branch, each of the first plurality of acousticwave resonators comprising an interdigital transducer electrodeinterposed between a pair of reflectors. A second plurality of acousticwave resonators is disposed over the piezoelectric layer and arranged inparallel, each of the second plurality of acoustic wave resonatorscomprising an interdigital transducer electrode interposed between apair of reflectors and being connected to the first branch and toground. A layer of negative temperature coefficient of frequencydielectric material is disposed over one or more of the second pluralityof acoustic wave resonators. Additional circuitry and the acoustic wavefilter are disposed on the package substrate.

In accordance with another aspect of the disclosure, a wirelesscommunication device is provided. The wireless communication devicecomprises an antenna and a front end module including an acoustic wavefilter configured to filter a radio frequency signal associated with theantenna. The acoustic wave filter includes a substrate, and apiezoelectric layer over the substrate. A first plurality of acousticwave resonators is disposed over the piezoelectric layer and arranged inseries along a first branch, each of the first plurality of acousticwave resonators comprising an interdigital transducer electrodeinterposed between a pair of reflectors. A second plurality of acousticwave resonators is disposed over the piezoelectric layer and arranged inparallel, each of the second plurality of acoustic wave resonatorscomprising an interdigital transducer electrode interposed between apair of reflectors and being connected to the first branch and toground. A layer of negative temperature coefficient of frequencydielectric material is disposed over one or more of the second pluralityof acoustic wave resonators.

In accordance with another aspect of the disclosure, an acoustic wavefilter is provided. The acoustic waive filter comprises a substrate anda piezoelectric layer disposed over the substrate. A first plurality ofacoustic wave resonators is disposed over the piezoelectric layer andarranged in series along a first branch, each of the first plurality ofacoustic wave resonators comprising an interdigital transducer electrodeinterposed between a pair of reflectors. A second plurality of acousticwave resonators is disposed over the piezoelectric layer and arranged inparallel, each of the second plurality of acoustic wave resonatorscomprising an interdigital transducer electrode interposed between apair of reflectors and being connected to the first branch and toground. A layer of positive temperature coefficient of frequencydielectric material is disposed over one or more of the first pluralityof acoustic wave resonators.

In accordance with another aspect of the disclosure, a radio frequencymodule is provided. The radio frequency module comprises a packagesubstrate and an acoustic wave filter configured to filter a radiofrequency signal. The acoustic wave filter includes a substrate, and apiezoelectric layer over the substrate. A first plurality of acousticwave resonators is disposed over the piezoelectric layer and arranged inseries along a first branch, each of the first plurality of acousticwave resonators comprising an interdigital transducer electrodeinterposed between a pair of reflectors. A second plurality of acousticwave resonators is disposed over the piezoelectric layer and arranged inparallel, each of the second plurality of acoustic wave resonatorscomprising an interdigital transducer electrode interposed between apair of reflectors and being connected to the first branch and toground. A layer of positive temperature coefficient of frequencydielectric material is disposed over one or more of the first pluralityof acoustic wave resonators. Additional circuitry and the acoustic wavefilter are disposed on the package substrate.

In accordance with another aspect of the disclosure, a wirelesscommunication device is provided. The wireless communication devicecomprises an antenna and a front end module including an acoustic wavefilter configured to filter a radio frequency signal associated with theantenna. The acoustic wave filter includes a substrate, and apiezoelectric layer over the substrate. A first plurality of acousticwave resonators is disposed over the piezoelectric layer and arranged inseries along a first branch, each of the first plurality of acousticwave resonators comprising an interdigital transducer electrodeinterposed between a pair of reflectors. A second plurality of acousticwave resonators is disposed over the piezoelectric layer and arranged inparallel, each of the second plurality of acoustic wave resonatorscomprising an interdigital transducer electrode interposed between apair of reflectors and being connected to the first branch and toground. A layer of positive temperature coefficient of frequencydielectric material is disposed over one or more of the first pluralityof acoustic wave resonators.

In accordance with another aspect of the disclosure, an acoustic wavefilter is provided. The acoustic waive filter comprises a substrate anda piezoelectric layer disposed over the substrate. A first plurality ofacoustic wave resonators is disposed over the piezoelectric layer andarranged in series along a first branch, each of the first plurality ofacoustic wave resonators comprising an interdigital transducer electrodeinterposed between a pair of reflectors. A second plurality of acousticwave resonators is disposed over the piezoelectric layer and arranged inparallel, each of the second plurality of acoustic wave resonatorscomprising an interdigital transducer electrode interposed between apair of reflectors and being connected to the first branch and toground. The interdigital transducer electrode of one or more of thesecond plurality of acoustic wave resonators has a wider duty factorthan the interdigital transducer electrode of the first plurality ofacoustic wave resonators.

In accordance with another aspect of the disclosure, a radio frequencymodule is provided. The radio frequency module comprises a packagesubstrate and an acoustic wave filter configured to filter a radiofrequency signal. The acoustic wave filter includes a substrate, and apiezoelectric layer over the substrate. A first plurality of acousticwave resonators is disposed over the piezoelectric layer and arranged inseries along a first branch, each of the first plurality of acousticwave resonators comprising an interdigital transducer electrodeinterposed between a pair of reflectors. A second plurality of acousticwave resonators is disposed over the piezoelectric layer and arranged inparallel, each of the second plurality of acoustic wave resonatorscomprising an interdigital transducer electrode interposed between apair of reflectors and being connected to the first branch and toground. The interdigital transducer electrode of one or more of thesecond plurality of acoustic wave resonators has a wider duty factorthan the interdigital transducer electrode of the first plurality ofacoustic wave resonators. Additional circuitry and the acoustic wavefilter are disposed on the package substrate.

In accordance with another aspect of the disclosure, a wirelesscommunication device is provided. The wireless communication devicecomprises an antenna and a front end module including an acoustic wavefilter configured to filter a radio frequency signal associated with theantenna. The acoustic wave filter includes a substrate, and apiezoelectric layer over the substrate. A first plurality of acousticwave resonators is disposed over the piezoelectric layer and arranged inseries along a first branch, each of the first plurality of acousticwave resonators comprising an interdigital transducer electrodeinterposed between a pair of reflectors. A second plurality of acousticwave resonators is disposed over the piezoelectric layer and arranged inparallel, each of the second plurality of acoustic wave resonatorscomprising an interdigital transducer electrode interposed between apair of reflectors and being connected to the first branch and toground. The interdigital transducer electrode of one or more of thesecond plurality of acoustic wave resonators has a wider duty factorthan the interdigital transducer electrode of the first plurality ofacoustic wave resonators.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will now be described, by way ofnon-limiting example, with reference to the accompanying drawings.

FIG. 1 is a schematic top view of an acoustic wave device.

FIG. 2 is a schematic cross-sectional view of the acoustic wave deviceof FIG. 1 .

FIG. 3 is a graph of frequency response for a resonator of the acousticwave device in FIG. 1 at different temperatures, the frequencynormalized relative to the resonant frequency.

FIG. 4 is a graph of frequency response for the acoustic wave device ofFIG. 1 at different temperatures, the frequency normalized relative tothe center passband frequency.

FIG. 5 is a schematic top view of an acoustic wave device.

FIG. 6 is a schematic cross-sectional view of the acoustic wave deviceof FIG. 5 .

FIG. 7 is a graph of frequency response for a resonator of the acousticwave device in FIG. 5 at different temperatures, the frequencynormalized relative to the resonant frequency.

FIG. 8 is a graph of frequency response for a resonator of the acousticwave device in FIG. 5 at different temperatures, the frequencynormalized relative to the resonant frequency.

FIG. 9 is a graph of frequency response for the acoustic wave device ofFIG. 5 at different temperatures, the frequency normalized relative tothe center passband frequency.

FIG. 10A shows a graphs of TCF versus cut angle for a series resonatorof the acoustic wave device of FIG. 5 .

FIG. 10B shows a graphs of TCF versus cut angle for a parallel or shuntresonator of the acoustic wave device of FIG. 5 .

FIG. 11A shows a graphs of TCF versus cut angle for a series resonatorof the surface wave device of FIG. 5 .

FIG. 11B shows a graphs of TCF versus cut angle for a parallel or shuntresonator of the acoustic wave device of FIG. 5 .

FIG. 12 is a schematic top view of an acoustic wave device.

FIG. 13 is a schematic cross-sectional view of the acoustic wave deviceof FIG. 12 .

FIG. 14 is a schematic top view of an acoustic wave device.

FIG. 15 is a schematic cross-sectional view of the acoustic wave deviceof FIG. 14 .

FIG. 16 is a schematic top view of an acoustic wave device.

FIG. 17 is a schematic cross-sectional view of the acoustic wave deviceof FIG. 16 .

FIG. 18 is a schematic top view of an acoustic wave device.

FIG. 19 is a schematic cross-sectional view of the acoustic wave deviceof FIG. 18 .

FIG. 20 is a schematic top view of an acoustic wave device.

FIG. 21 is a schematic cross-sectional view of the acoustic wave deviceof FIG. 20 .

FIG. 22 is a schematic top view of an acoustic wave device.

FIG. 23 is a schematic cross-sectional view of the acoustic wave deviceof FIG. 22 .

FIG. 24 is a schematic top view of an acoustic wave device.

FIG. 25 is a schematic cross-sectional view of the acoustic wave deviceof FIG. 24 .

FIG. 26 is a schematic block diagram of a packaged module that includesa filter with an acoustic wave device according to an embodiment.

FIG. 27 is a schematic block diagram of a packaged module that includesa filter with an acoustic wave device according to another embodiment.

FIG. 28A is a schematic block diagram of a wireless communication devicethat includes a filter with an acoustic wave device according to anembodiment.

FIG. 28B is a schematic block diagram of a wireless communication devicethat includes a filter with an acoustic wave device according to anotherembodiment.

DETAILED DESCRIPTION

The following description of certain embodiments presents variousdescriptions of specific embodiments. However, the innovations describedherein can be embodied in a multitude of different ways, for example, asdefined and covered by the claims. In this description, reference ismade to the drawings where like reference numerals can indicateidentical or functionally similar elements. It will be understood thatelements illustrated in the figures are not necessarily drawn to scale.Moreover, it will be understood that certain embodiments can includemore elements than illustrated in a drawing and/or a subset of theelements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

FIG. 1 is a schematic top view of an acoustic wave device 30. In oneimplementation, the acoustic wave device is a ladder filter with one ormore resonators 12 arranged in a series 10 (e.g., series resonators 12on a series arm) and one or more resonators 22 arranged in parallel 20(e.g., in parallel arm(s)). The one or more resonators 22 connect toground 40 so the one or more resonators 22 can be shunt resonators 22and the one or more parallel arms can be shunt arms. Each of theresonators 22 can include an interdigital transducer (IDT) electrode 34with a plurality of fingers 35 and reflectors 24 on opposite sides ofthe IDT electrode 34. Similarly, each of the resonators 12 can includean interdigital transducer (IDT) electrode 36 with a plurality offingers 37 and reflectors 14 on opposite sides of the IDT electrode 36.In one implementation, the resonators 12, 22 are surface acoustic wave(SAW) resonators. However, in other implementations, the resonators 12,22 can be a bulk acoustic wave (BAW) resonators. In the illustratedimplementation, the resonators 12, 22 are identical.

FIG. 2 shows a schematic cross-sectional view of the acoustic wavedevice 30. The acoustic wave device 30 can have a multilayerpiezoelectric substrate structure. As shown in FIG. 2 , the acousticwave device 30 includes a substrate structure (e.g., substrate, layer)31, an additional structure (e.g., substrate, functional layer) 32 over(e.g., disposed over, disposed adjacent to, disposed in contact with)the substrate structure 31, a piezoelectric structure (e.g., layer) 33over (e.g., disposed over, disposed adjacent to, disposed in contactwith) the additional structure 32, and interdigital transducer (IDT)electrodes 34, 36 with fingers 35, 37, respectively, over (e.g.,disposed over, disposed adjacent to, disposed in contact with) thepiezoelectric structure 33. For simplicity, FIG. 2 shows a partial viewof the IDT electrodes 34, 36, showing portions representing the fingers35, 37 of the IDT electrodes 34, 36 of the acoustic wave device 30(e.g., ladder filter). In some implementations, the additional structure(e.g., substrate, functional layer) 32 is excluded (e.g., thepiezoelectric structure or layer 33 is disposed over, adjacent to and/orin contact with the substrate structure or layer 31).

The piezoelectric layer 33 can be a lithium based piezoelectric layer.For example, the piezoelectric layer 33 can be a lithium tantalate(LiTaO3) layer. As another example, the piezoelectric layer 33 can be alithium niobate (LiNbO3) layer. The piezoelectric layer 33 has anegative temperature coefficient of frequency (TCF). The IDT electrode34, 36 can include Aluminum (Al), molybdenum (Mo), tungsten (W), gold(Au), silver (Ag), copper (Cu), platinum (Pt), ruthenium (Ru), titanium(Ti), the like, or any suitable combination thereof. In someimplementations, the IDT electrode 34, 36 can be a multi-layer IDT. Forexample, the IDT electrode 34, 36 can have a first layer of Aluminum,and a second layer of molybdenum. In another example, the IDT electrode34, 36 can have a first layer of Aluminum, and a second layer oftungsten. In another example, the IDT electrode 34, 36 can have a firstlayer of Aluminum, and a second layer of platinum. In someimplementations, the IDT electrode 34, 36, whether single later ormulti-layer, can be covered by a dielectric layer, such as of silicondioxide (SiO2) and/or have a protective layer, such as of siliconnitride (SiN).

The additional structure (e.g., layer, functional layer) 32 can have alower acoustic impedance than the substrate structure (e.g., layer) 31.The additional structure (e.g., layer) 32 can increase adhesion betweenthe substrate structure 31 and the piezoelectric structure 33 of themulti-layer piezoelectric substrate. Alternatively or additionally, theadditional structure (e.g., layer) 32 can increase heat dissipation inthe SAW device 30 relative to the SAW device 20. The additional orfunctional layer 32 can be made of silicon dioxide (SiO2).

In one implementation, the substrate structure (e.g., layer) 31 can beformed or provided. The additional layer or structure (e.g., functionallayer) 32 can be formed or provided (e.g., disposed on, attached oradhered to the substrate structure 31). The piezoelectric structure(e.g., layer) 33 can be formed or provided (e.g., disposed on, attachedor adhered to the additional layer 32). The IDT electrodes 34, 36 can beformed or provided (e.g., disposed on, attached or adhered to thepiezoelectric structure or layer 33).

FIG. 3 shows the frequency response for the resonators 12 (e.g., seriesresonators 12), normalized relative to the resonant frequency. The graphof FIG. 3 shows that the anti-resonant frequency has a near zerotemperature coefficient of frequency (TCF), but the resonant frequencyhas a positive temperature coefficient of frequency (TCF)—that is itincreases in electrical resistance with increased temperature. FIG. 4shows the frequency response for the acoustic wave device 30, normalizedrelative to the passband center frequency. The upper edge of the band orhigher slope TCF is almost zero, whereas the lower edge of the band orlower slope TCF is worse because the resonant frequency TCF for theresonators 12 has a positive value. This can lead to degradedattenuation for the acoustic wave device 30 a lower temperatures.

FIGS. 5-6 show an acoustic wave device 30A. The acoustic wave device 30Ais similar to the acoustic wave device 30 of FIGS. 1-2 . Thus, referencenumerals used to designate the various components of the acoustic wavedevice 30A are identical to those used for identifying the correspondingcomponents of the acoustic wave device 30 in FIGS. 1-2 , except that an“A” has been added to the numerical identifier. Therefore, the structureand description for the various features and components of the acousticwave device 30 in FIGS. 1-2 are understood to also apply to thecorresponding features of the acoustic wave device 30A in FIGS. 5-6 ,except as described below.

The acoustic wave device 30A differs from the acoustic wave device 30 inFIGS. 1-2 in that the resonators 22A (e.g., shunt resonators 22A) arecovered (e.g., the IDT electrode 34A and reflectors 24A are covered)with a film 50A (e.g., one or more layer(s), structure) of negativetemperature coefficient of frequency (TCF) dielectric material. Theresonators 12A (e.g., series resonators 12A) are uncovered (e.g., notcovered by a film or layer, for example of negative TCF dielectricmaterial). In one example, the film 50A can be of silicon nitride (SiN).In another example, the film 50A can be of zinc oxide (ZnO). In anotherexample, the film 50A can be of silicon oxynitride (SiON). However, thefilm 50A can be of other suitable materials with negative TCF. In theillustrated implementation, each of the resonators 22A is covered by aseparate film 50A. In another implementation, two or more (e.g., all) ofthe resonators 22A (e.g., shunt resonators 22A) are covered by the samefilm 50A. The film 50A can be formed or provided (e.g., disposed on,attached or adhered to the piezoelectric structure or layer 33 and theIDT electrode 34A and reflectors 24A). The film 50A can be etched orotherwise machined to a desired height above the piezoelectric structureor layer 33.

The substrate structure or layer 31A can include (e.g., be made of,consist of) silicon (Si). In another example, the substrate structure orlayer 31A can be made of poly-silicon. In another example, the substratestructure or layer 31A can be made of amorphous silicon. In anotherexample, the substrate structure or layer 31A can be made of siliconnitride (SiN). In another example, the substrate structure or layer 31Acan be made of Sapphire. In another example, the substrate structure orlayer 31A can be made of quartz. In another example, the substratestructure or layer 31A can be made of aluminum nitride (AlN). In anotherexample, the substrate structure or layer 31A can be made ofpolycrystalline ceramic (Mg₂O₄). In another implementation, thesubstrate structure or layer 31A can be made of diamond. However, thesubstrate structure or layer 31A can be made of other suitable highimpedance materials. An acoustic impedance of the substrate structure31A can be higher than an acoustic impedance of the piezoelectricstructure (e.g., layer) 33A.

FIG. 7 shows the frequency response for the resonators 22A, normalizedrelative to the resonant frequency. The graph of FIG. 7 shows that theresonant frequency has a near zero temperature coefficient of frequency(TCF), but the anti-resonant frequency has a negative temperaturecoefficient of frequency (TCF)—that is it decreases in electricalresistance with increased temperature. FIG. 8 shows the frequencyresponse for the resonators 12A (e.g., series resonators 12A),normalized relative to the resonant frequency. The graph of FIG. 8 showsthat the resonant frequency has a positive temperature coefficient offrequency (TCF), but the anti-resonant frequency has a near zerotemperature coefficient of frequency (TCF). FIG. 9 shows the frequencyresponse for the acoustic wave device 30A, normalized relative to thepassband center frequency. The graph of FIG. 9 shows that the upper edgeof the band or higher slope TCF is almost zero, whereas the lower edgeof the band or lower slope TCF is improved (e.g., is closer to zero TCFso does not vary with temperature). Accordingly, the acoustic wavedevice 30A has improved temperature stability relative to the acousticwave device 30 (e.g., adjusts or tunes the TCF of the resonant andanti-resonant frequency to be substantially the same).

FIGS. 10A and 10B show graphs of temperature coefficient of frequency(TCF) for the series resonators 12A (TCFs) and for the parallel or shuntresonators 22A (TCFp) where the additional layer or structure (e.g.,functional layer) 32 is made of silicon dioxide (SiO₂) and has athickness of 0.3 L, where L is the pitch between the fingers 35A, 37A ofthe IDTs 34A, 36A. The graphs show that TCFs and TCFp vary with thethickness of the piezoelectric structure or layer 33A, where thepiezoelectric structure or layer is made of lithium tantalate (LiTaO3).As shown in the graphs, TCFs is higher than TCFp, and the TCFs valuesfor the series resonators 12A become positive when the thickness of thepiezoelectric structure or layer 33A becomes thinner than 0.3 L.

FIGS. 11A and 11B show graphs of temperature coefficient of frequency(TCF) for the series resonators 12A (TCFs) and for the parallel or shuntresonators 22A (TCFp) where the additional layer or structure (e.g.,functional layer) 32 is made of silicon dioxide (SiO₂) and has athickness of 0.2 L, where L is the pitch between the fingers 35A, 37A ofthe IDTs 34A, 36A. The graphs show that TCFs and TCFp vary with thethickness of the piezoelectric structure or layer 33A, where thepiezoelectric structure or layer is made of lithium tantalate (LiTaO3).As shown in the graphs, TCFs is higher than TCFp, and the TCFs valuesfor the series resonators 12A become positive when the thickness of thepiezoelectric structure or layer 33A becomes thinner than 0.3 L.

FIGS. 12-13 show an acoustic wave device 30B. The acoustic wave device30B is similar to the acoustic wave device 30A of FIGS. 5-6 . Thus,reference numerals used to designate the various components of theacoustic wave device 30B are identical to those used for identifying thecorresponding components of the acoustic wave device 30A in FIGS. 5-6 ,except that a “B” instead of an “A” has been added to the numericalidentifier. Therefore, the structure and description for the variousfeatures and components of the acoustic wave device 30A in FIGS. 5-6(which is based on the structure and description for the acoustic wavedevice 30 in FIGS. 1-2 ) are understood to also apply to thecorresponding features of the acoustic wave device 30B in FIGS. 12-13 ,except as described below.

The acoustic wave device 30B differs from the acoustic wave device 30Ain FIGS. 5-6 in that the resonators 12B (e.g., series resonators 12B)are covered (e.g., the IDT 36B and reflectors 14B are covered) with afilm 50B of positive temperature coefficient of frequency (TCF)dielectric material, and the resonators 22B (e.g., shunt resonators 22B)are uncovered (e.g., the IDT 34B and reflectors 24B are not covered witha film, for example, of negative or positive TCF dielectric material).In one example, the film 50B can be of silicon dioxide (SiO₂). In theillustrated implementation, each of the resonators 12B is covered by aseparate film 50B of positive TCF material. In another implementation,two or more (e.g., all) of the resonators 12B (e.g., series resonators12B) are covered by the same film 50B of positive TCF material. Coveringthe series resonators 12B with the film 50B of positive TCF material hasa similar effect as covering the shunt resonators 22A with the film 50Aof negative TCF material—that is, it improves the temperature stabilityof the acoustic wave device 30B (e.g., synchronizes the resonant andanti-resonant TCF on each of the series resonators 12B and shuntresonators 22B).

FIGS. 14-15 show an acoustic wave device 30C. The acoustic wave device30C is similar to the acoustic wave device 30A of FIGS. 5-6 . Thus,reference numerals used to designate the various components of theacoustic wave device 30C are identical to those used for identifying thecorresponding components of the acoustic wave device 30A in FIGS. 5-6 ,except that a “C” instead of an “A” has been added to the numericalidentifier. Therefore, the structure and description for the variousfeatures and components of the acoustic wave device 30A in FIGS. 5-6(which is based on the structure and description for the acoustic wavedevice 30 in FIGS. 1-2 ) are understood to also apply to thecorresponding features of the acoustic wave device 30C in FIGS. 14-15 ,except as described below.

The acoustic wave device 30C differs from the acoustic wave device 30Ain FIGS. 5-6 in that not all of the shunt resonators 22C are covered bythe film 50C of negative TCF dielectric material (e.g., one or more ofthe shunt resonators 22C are covered by the film 50C). In theillustrated example, one shunt resonator 22C is not covered by the film50C and the other two shunt resonators 22C are covered by the film 50 ofnegative TCF material. The resonators 12C (e.g., series resonators 12C)are uncovered (e.g., not covered by a film or layer, for example ofnegative TCF dielectric material). Covering some (but not all) of theshunt resonators 22C with the negative TCF material film 50C results inan improved temperature stability of the acoustic wave device 30C ascompared to the acoustic wave device 30 (e.g., adjusts or tunes the TCFof the resonant and anti-resonant frequency to be approximately thesame).

FIGS. 16-17 show an acoustic wave device 30D. The acoustic wave device30D is similar to the acoustic wave device 30 of FIGS. 1-2 . Thus,reference numerals used to designate the various components of theacoustic wave device 30D are identical to those used for identifying thecorresponding components of the acoustic wave device 30 in FIGS. 1-2 ,except that a “D” has been added to the numerical identifier. Therefore,the structure and description for the various features and components ofthe acoustic wave device 30 in FIGS. 1-2 are understood to also apply tothe corresponding features of the acoustic wave device 30D in FIGS.16-17 , except as described below.

The acoustic wave device 30D differs from the acoustic wave device 30 inFIGS. 1-2 in that one or more of the shunt resonators 22D have an IDTelectrode 34D with fingers 35D that have a width W2 that is greater thana width W1 of the fingers 37D of the IDT electrode 36D of the seriesresonators 12D. Accordingly, one or more of the shunt resonators 22Dhave a wider duty factor (DF) than the series resonators 12D. Theresonators 12D (e.g., series resonators 12D) and resonators 22D (e.g.,shunt resonators 22D) are uncovered (e.g., not covered by a film orlayer of positive or negative TCF dielectric material). The material ofthe IDT electrodes 34D (e.g., metal) has a negative temperaturecoefficient of frequency (TCF), so the one or more shunt resonators 22Dwith the wider duty factor (DF) have a higher negative TCF value, whichresults in an improved temperature stability of the acoustic wave device30D as compared to the acoustic wave device 30 (e.g., adjusts or tunesthe TCF of the resonant and anti-resonant frequency to be approximatelythe same). In another implementation, a similar effect is provided byhaving one or more of the shunt resonators 22D have an IDT electrode 34Dwith fingers 35D that have a width W2 that is smaller than a width W1 ofthe fingers 37D of the IDT electrode 36D of the series resonators 12D.

FIGS. 18-19 show an acoustic wave device 30E. The acoustic wave device30E is similar to the acoustic wave device 30C of FIGS. 14-15 . Thus,reference numerals used to designate the various components of theacoustic wave device 30E are identical to those used for identifying thecorresponding components of the acoustic wave device 30C in FIGS. 14-15, except that an “E” instead of a “C” has been added to the numericalidentifier. Therefore, the structure and description for the variousfeatures and components of the acoustic wave device 30C in FIGS. 14-15(which is based on the structure and description for the acoustic wavedevice 30 in FIGS. 1-2 ) are understood to also apply to thecorresponding features of the acoustic wave device 30E in FIGS. 18-19 ,except as described below.

The acoustic wave device 30E differs from the acoustic wave device 30Cin FIGS. 14-15 in that the series resonators 12E and at least one of theshunt resonators 22E are covered by the film 52E of negative TCFdielectric material having a height or thickness H2 that is smaller thana height or thickness H1 of the film 50E of negative TCF dielectricmaterial that covers the remaining shunt resonators 22E. In theillustrated implementation, each of the series resonators 12E is coveredby a separate film 52E and each of the shunt resonators 22E is coveredby a separate film 50E or 52E. In another implementation, two or more(e.g., all) of the resonators 12E (e.g., series resonators 12E) arecovered by the same film 52E and/or two or more (e.g., all) of theresonators 22E (e.g., shunt resonators 22E) are covered by the same film50E. The greater thickness H1 of the film 50E that covers one or more ofthe shunt resonators 22E provides them with a higher negative TCF value(e.g., than that for the resonators 12E, 22E covered by the film 52E),which results in an improved temperature stability of the acoustic wavedevice 30E (e.g., adjusts or tunes the TCF of the resonant andanti-resonant frequency to be approximately the same).

FIGS. 20-21 show an acoustic wave device 30F. The acoustic wave device30F is similar to the acoustic wave device 30E of FIGS. 18-19 . Thus,reference numerals used to designate the various components of theacoustic wave device 30F are identical to those used for identifying thecorresponding components of the acoustic wave device 30E in FIGS. 18-19, except that an “F” instead of a “E” has been added to the numericalidentifier. Therefore, the structure and description for the variousfeatures and components of the acoustic wave device 30E in FIGS. 18-19(which is based on the structure and description for the acoustic wavedevice 30 in FIGS. 1-2 ) are understood to also apply to thecorresponding features of the acoustic wave device 30F in FIGS. 20-21 ,except as described below.

The acoustic wave device 30F differs from the acoustic wave device 30Ein FIGS. 18-19 in that the resonators 12F (e.g., series resonators 12F)and at least one shunt resonator 22F are covered (e.g., the IDT 36F andreflectors 14F are covered) with a film 52F of positive temperaturecoefficient of frequency (TCF) dielectric material, and the remainingresonators 22F (e.g., shunt resonators 22F) are covered (e.g., the IDT34F and reflectors 24F are covered) with a film 50F of positivetemperature coefficient of frequency (TCF) dielectric material. Theheight or thickness H2 of the film 52F is greater than the height orthickness H1 of the film 50F. Covering the series resonators 12F and atleast one shunt resonator 22F with the film 52F of positive TCFdielectric material having thickness H2, and covering the remainingshunt resonators 22F with the film 50F of positive TCF dielectricmaterial having thickness H1 has a similar effect as the films 50E, 52Eused for the acoustic wave device 30E—that is, it improves thetemperature stability of the acoustic wave device 30F (e.g.,synchronizes the resonant and anti-resonant TCF of the series resonators12F and shunt resonators 22F).

FIGS. 22-23 show an acoustic wave device 30G. The acoustic wave device30G is similar to the acoustic wave device 30E of FIGS. 18-19 . Thus,reference numerals used to designate the various components of theacoustic wave device 30G are identical to those used for identifying thecorresponding components of the acoustic wave device 30E in FIGS. 18-19, except that a “G” instead of a “E” has been added to the numericalidentifier. Therefore, the structure and description for the variousfeatures and components of the acoustic wave device 30E in FIGS. 18-19(which is based on the structure and description for the acoustic wavedevice 30 in FIGS. 1-2 ) are understood to also apply to thecorresponding features of the acoustic wave device 30G in FIGS. 22-23 ,except as described below.

The acoustic wave device 30G differs from the acoustic wave device 30Ein FIGS. 18-19 in that a film 52G of negative TCF dielectric materialhaving a height or thickness H2 covers all of the series resonators 12Gand all of the shunt resonators 22G, and an additional film 50G (e.g.,or portion, layer or structure) of negative TCF dielectric materialcovers one or more (e.g., two) of the shunt resonators 22G (e.g., thefilm 50G extending over the film 52G) so that the negative TCFdielectric material that covers the one or more shunt resonators 22G hasa total height or thickness H1 that is greater than the height orthickness H2. Additionally, one or more of the shunt resonators 22G hasan IDT electrode 34G with fingers 35G that have a width W2 that isgreater than a width W12 of the fingers 37G of the IDT electrode 36G ofthe series resonators 12G. The material of the IDT electrodes 34G (e.g.,metal) has a negative temperature coefficient of frequency (TCF), so theone or more shunt resonators 22G with the wider duty factor (DF) have ahigher negative TCF value. The wider duty factor (DF) and the thickerfilm layer or structure 50G covering the shunt resonators 22G result inan improved temperature stability of the acoustic wave device 30G ascompared to the acoustic wave device 30E (e.g., adjusts or tunes the TCFof the resonant and anti-resonant frequency to be approximately thesame).

FIGS. 24-25 show an acoustic wave device 30H. The acoustic wave device30H is similar to the acoustic wave device 30G of FIGS. 22-23 . Thus,reference numerals used to designate the various components of theacoustic wave device 30H are identical to those used for identifying thecorresponding components of the acoustic wave device 30G in FIGS. 22-23, except that an “H” instead of a “G” has been added to the numericalidentifier. Therefore, the structure and description for the variousfeatures and components of the acoustic wave device 30G in FIGS. 22-23(which is based on the structure and description for the acoustic wavedevice 30 in FIGS. 1-2 ) are understood to also apply to thecorresponding features of the acoustic wave device 30H in FIGS. 24-25 ,except as described below.

The acoustic wave device 30F differs from the acoustic wave device 30Gin FIGS. 22-23 in that the film 52H with the height or thickness H2 thatcovers all of the series resonators 12H and all of the shunt resonators22H is of a positive temperature coefficient of frequency (TCF)dielectric material, and the additional film 50H (e.g., or portion,layer or structure) is of a positive TCF dielectric material and coversone or more of the series resonators 12H (e.g., and does not cover anyof the shunt resonators 22H) so that the positive TCF dielectricmaterial that covers the one or more series resonators 12H has a totalheight or thickness H1 that is greater than the height or thickness H2.One or more of the shunt resonators 22H have an IDT electrode 34H withfingers 35H can have a width W1 that is smaller than a width W2 of thefingers 37H of the IDT electrode 36H of the series resonators 12H.

Covering the series resonators 12H and shunt resonator 22H with the film52H of positive TCF dielectric material having thickness H2, andcovering one or more of the series resonators 12H with the film 50H ofpositive TCF dielectric material, as well as having at least one of theseries resonators 12H have a wider duty factor (DF) than the seriesresonators 12H, has a similar effect as the films 50G, 52G used for theacoustic wave device 30G—that is, it improves the temperature stabilityof the acoustic wave device 30H (e.g., synchronizes the resonant andanti-resonant TCF of the series resonators 12H and shunt resonators22H).

The surface acoustic wave device 30-30H and/or other acoustic wavedevices disclosed herein can be included in a band pass filter. The bandpass filter can have a passband with a center frequency in a range from1.5 gigahertz (GHz) to 2.5 GHz. The center frequency can be anarithmetic mean or a geometric mean of a lower cutoff frequency of thepassband and an upper cutoff frequency of the passband. The centerfrequency in a range from 1.5 GHz to 2.2 GHz in certain instances. Thepassband can have a bandwidth in a range from 5 megahertz (MHz) to 100MHz in certain applications. The band pass filter can have a passbanddefined by a communication standard in which the passband is within afrequency range from 1.5 GHz to 2.5 GHz.

In some instances, the surface acoustic wave device 30-30H and/or otheracoustic wave devices disclosed herein can be included in a band stopfilter having a center frequency in a range from 1.5 GHz to 2.5 GHz. Thestop band of the band stop filter can have a bandwidth in a range from 5MHz to 100 MHz in certain applications.

The acoustic wave devices disclosed herein can be implemented in avariety of packaged modules. An example packaged module will now bedescribed in which any suitable principles and advantages of theacoustic wave resonators disclosed herein can be implemented. A packagedmodule can include one or more features of the packaged module of FIG.26 and/or the packaged module of FIG. 27 .

FIG. 26 is a schematic block diagram of a module 90 that includes afilter 92 with one or more acoustic wave devices in accordance with anysuitable principles and advantage disclosed herein. The module 90includes the filter 92 that includes the one or more acoustic wavedevices, a switch 94, a power amplifier 95, and a radio frequency (RF)coupler 96. The power amplifier 95 can amplify a radio frequency signal.The switch 94 can selectively electrically couple an output of the poweramplifier 95 to the filter 92. The filter 92 can be a band pass filter.The filter 92 can be included in a duplexer or other multiplexer. The RFcoupler 96 can be a directional coupler or any other suitable RFcoupler. The RF coupler 96 can sample a portion of RF power in atransmit signal path and provide an indication of the RF power. The RFcoupler 96 can be coupled to the transmit signal path in any suitablepoint, such as between an output of the power amplifier 95 and an inputto the switch 94. The module 90 can include a package that encloses theillustrated elements. The filter 92 with the acoustic wave resonator canbe disposed on a common packaging substrate 97 with the otherillustrated elements of the module 90. The packaging substrate 97 can bea laminate substrate, for example.

FIG. 27 is a schematic block diagram of a module 100 that includesfilters 102 that include one or more acoustic wave devices in accordancewith any suitable principles and advantage disclosed herein. Asillustrated, the module 100 includes a power amplifier 95, a switch 94,filters 102, an antenna switch 104, a switch 105, a low noise amplifier106, and a control circuit 107.

The power amplifier 95 can receive a radio frequency signal from atransmit port TX. In some instances, a switch can electrically connect aselected one of a plurality of transmit ports to an input of the poweramplifier 95. The power amplifier 95 can operate in an envelope trackingmode and/or an average power tracking mode. The switch 94 can be amulti-throw radio frequency switch configured to electrically connect anoutput of the power amplifier 95 to one or more selected transmitfilters of the filters 102. The switch 94 can be a band select switcharranged to electrically connect the output of the power amplifier 95 toa transmit filter for a particular frequency band.

The filters 102 can be acoustic wave filters (e.g., ladder filters). Oneor more resonators in any of the filters 102 can include a negative TCFfilm or a positive TCF film and/or a wider duty factor (DF) inaccordance with any suitable principles and advantages disclosed herein.The filters 102 can include a plurality of duplexers and/or othermultiplexers. Alternatively or additionally, the filters 102 can includeone or more standalone transmit filters and/or one or more standalonereceive filters. The filters 102 can include at least four duplexers insome applications. According to some other applications, the filters 102can include at least eight duplexers.

As illustrated, the filters 102 are electrically connected to theantenna switch 104. The antenna switch 104 can be a multi-throw radiofrequency switch arranged to electrically connect one or more filters ofthe filters 102 to an antenna port ANT of the module 100. The antennaswitch 104 can include at least eight throws in some applications. Incertain applications, the antenna switch 104 can include at least tenthrows.

A switch 105 can electrically connect a selected receive filter of thefilters to a low noise amplifier 106. The low noise amplifier 106 isarranged to amplify the received radio frequency signal and provide anoutput to a receive port RX. In some instances, another switch can beelectrically coupled between the low noise amplifier 106 and the receiveport RX.

The illustrated module 100 also includes a control circuit 107. Thecontrol circuit 107 can perform any suitable control functions for themodule 100.

FIG. 28A is a schematic block diagram of a wireless communication device110 that includes a filter 113 with an acoustic wave device inaccordance with one or more embodiments. The wireless communicationdevice 110 can be any suitable wireless communication device. Forinstance, a wireless communication device 110 can be a mobile phone,such as a smart phone. As illustrated, the wireless communication device110 includes an antenna 111, an RF front end 112, an RF transceiver 114,a processor 115, a memory 116, and a user interface 117. The antenna 111can transmit RF signals provided by the RF front end 112. The antenna111 can provide received RF signals to the RF front end 112 forprocessing.

The RF front end 112 can include one or more power amplifiers, one ormore low noise amplifiers, one or more RF switches, one or more receivefilters, one or more transmit filters, one or more duplex filters, oneor more filters of a multiplexer, one or more filters of a diplexer orother frequency multiplexing circuit, or any suitable combinationthereof. The RF front end 112 can transmit and receive RF signalsassociated with any suitable communication standard. Any of the acousticresonators disclosed herein can be implemented in filter 113 of the RFfront end 112.

The RF transceiver 114 can provide RF signals to the RF front end 112for amplification and/or other processing. The RF transceiver 114 canalso process an RF signal provided by a low noise amplifier of the RFfront end 112. The RF transceiver 114 is in communication with theprocessor 115. The processor 115 can be a baseband processor. Theprocessor 115 can provide any suitable base band processing functionsfor the wireless communication device 110. The memory 116 can beaccessed by the processor 115. The memory 116 can store any suitabledata for the wireless communication device 110. The processor 115 isalso in communication with the user interface 117. The user interface117 can be any suitable user interface, such as a display.

FIG. 28B is a schematic block diagram of a wireless communication device120 that includes a radio frequency front end 112 with a filter 113 anda diversity receive module 122 with a filter 123 according to anembodiment. The wireless communication device 120 is like the wirelesscommunication device 110 of FIG. 28A, except that the wirelesscommunication device 120 also includes diversity receive features. Asillustrated in FIG. 28B, the wireless communication device 120 includesa diversity antenna 121, a diversity receive module 122 configured toprocess signals received by the diversity antenna 121 and includingfilters 123, and a transceiver 124 in communication with both the radiofrequency front end 112 and the diversity receive module 122. The filter103 can include one or more ladder filters as disclosed herein.

Any of the embodiments described above can be implemented in associationwith mobile devices such as cellular handsets. The principles andadvantages of the embodiments can be used for any systems or apparatus,such as any uplink wireless communication device, that could benefitfrom any of the embodiments described herein. The teachings herein areapplicable to a variety of systems. Although this disclosure includessome example embodiments, the teachings described herein can be appliedto a variety of structures. Any of the principles and advantagesdiscussed herein can be implemented in association with RF circuitsconfigured to process signals in a frequency range from about 30kilohertz (kHz) to 300 gigahertz (GHz), such as in a frequency rangefrom about 450 MHz to 8.5 GHz. An acoustic wave resonator including anysuitable combination of features disclosed herein be included in afilter arranged to filter a radio frequency signal in a fifth generation(5G) New Radio (NR) operating band within Frequency Range 1 (FR1). Afilter arranged to filter a radio frequency signal in a 5G NR operatingband can include one or more acoustic wave resonators disclosed herein.FR1 can be from 410 MHz to 7.125 GHz, for example, as specified in acurrent 5G NR specification. One or more acoustic wave resonators inaccordance with any suitable principles and advantages disclosed hereincan be included in a filter arranged to filter a radio frequency signalin a fourth generation (4G) Long Term Evolution (LTE) operating band.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products such as packaged radio frequency modules, uplinkwireless communication devices, wireless communication infrastructure,electronic test equipment, etc. Examples of the electronic devices caninclude, but are not limited to, a mobile phone such as a smart phone, awearable computing device such as a smart watch or an ear piece, atelephone, a television, a computer monitor, a computer, a modem, ahand-held computer, a laptop computer, a tablet computer, a microwave, arefrigerator, a vehicular electronics system such as an automotiveelectronics system, a stereo system, a digital music player, a radio, acamera such as a digital camera, a portable memory chip, a washer, adryer, a washer/dryer, a copier, a facsimile machine, a scanner, amulti-functional peripheral device, a wrist watch, a clock, etc.Further, the electronic devices can include unfinished products.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,”“include,” “including” and the like are to be construed in an inclusivesense, as opposed to an exclusive or exhaustive sense; that is to say,in the sense of “including, but not limited to.” The word “coupled”, asgenerally used herein, refers to two or more elements that may be eitherdirectly connected, or connected by way of one or more intermediateelements. Likewise, the word “connected”, as generally used herein,refers to two or more elements that may be either directly connected, orconnected by way of one or more intermediate elements. Additionally, thewords “herein,” “above,” “below,” and words of similar import, when usedin this application, shall refer to this application as a whole and notto any particular portions of this application. Where the contextpermits, words in the above Detailed Description using the singular orplural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel apparatus, methods, andsystems described herein may be embodied in a variety of other forms;furthermore, various omissions, substitutions and changes in the form ofthe methods and systems described herein may be made without departingfrom the spirit of the disclosure. Any suitable combination of theelements and acts of the various embodiments described above can becombined to provide further embodiments. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. An acoustic wave filter comprising: a substrate; a piezoelectric layer disposed over the substrate; a first plurality of acoustic wave resonators disposed over the piezoelectric layer and arranged in series along a first branch, each of the first plurality of acoustic wave resonators including an interdigital transducer electrode interposed between a pair of reflectors; and a second plurality of acoustic wave resonators disposed over the piezoelectric layer and arranged in parallel, each of the second plurality of acoustic wave resonators including an interdigital transducer electrode interposed between a pair of reflectors and being connected to the first branch and to ground, the interdigital transducer electrode of one or more of the second plurality of acoustic wave resonators having a wider duty factor than the interdigital transducer electrode of the first plurality of acoustic wave resonators.
 2. The acoustic wave filter of claim 1 wherein the first plurality of acoustic wave resonators and the second plurality of acoustic wave resonators are surface acoustic wave resonators.
 3. The acoustic wave filter of claim 1 wherein an additional layer is disposed between the substrate and the piezoelectric layer, the additional layer having a lower acoustic impedance than the substrate and configured to facilitate adhesion between the substrate and the piezoelectric layer.
 4. The acoustic wave filter of claim 3 wherein the additional layer is of silicon dioxide (SiO₂).
 5. The acoustic wave filter of claim 1 wherein the piezoelectric layer includes one or more of lithium tantalate, lithium niobate.
 6. The acoustic wave filter of claim 1 wherein the substrate includes one of silicon, poly-silicon, amorphous silicon, silicon nitride (SiN), Sapphire, quartz, aluminum nitride (AlN) or polycrystalline ceramic (Mg₂O₄).
 7. The acoustic wave filter of claim 1 wherein a layer of negative temperature coefficient of frequency dielectric material is disposed over one or more of the second plurality of acoustic wave resonators.
 8. The acoustic wave filter of claim 7 wherein a second layer of negative temperature coefficient of frequency dielectric material is disposed over each of the first plurality of acoustic wave resonators and has a height above the substrate that is smaller than a height of the layer of negative temperature coefficient of frequency dielectric material disposed over said one or more of the second plurality of acoustic wave resonators.
 9. The acoustic wave filter of claim 8 wherein the second layer of negative temperature coefficient of frequency dielectric material is a single continuous layer that covers the first plurality of acoustic wave resonators and the second plurality of acoustic wave resonators, the layer of negative temperature coefficient of frequency dielectric material being disposed over the second layer of negative temperature coefficient of frequency dielectric material.
 10. A radio frequency module comprising: a package substrate; an acoustic wave filter configured to filter a radio frequency signal, the acoustic wave filter including a substrate, a piezoelectric layer over the substrate, a first plurality of acoustic wave resonators disposed over the piezoelectric layer and arranged in series along a first branch, each of the first plurality of acoustic wave resonators including an interdigital transducer electrode interposed between a pair of reflectors, a second plurality of acoustic wave resonators disposed over the piezoelectric layer and arranged in parallel, each of the second plurality of acoustic wave resonators including an interdigital transducer electrode interposed between a pair of reflectors and being connected to the first branch and to ground, the interdigital transducer electrode of one or more of the second plurality of acoustic wave resonators having a wider duty factor than the interdigital transducer electrode of the first plurality of acoustic wave resonators; and additional circuitry, the acoustic wave filter and additional circuitry disposed on the package substrate.
 11. The radio frequency module of claim 10 wherein the first plurality of acoustic wave resonators and the second plurality of acoustic wave resonators are surface acoustic wave resonators.
 12. The radio frequency module of claim 10 wherein an additional layer is disposed between the substrate and the piezoelectric layer, the additional layer having a lower acoustic impedance than the substrate and configured to facilitate adhesion between the substrate and the piezoelectric layer.
 13. The radio frequency module of claim 10 wherein a layer of negative temperature coefficient of frequency dielectric material is disposed over one or more of the second plurality of acoustic wave resonators.
 14. The radio frequency module of any of claims 13 wherein a second layer of negative temperature coefficient of frequency dielectric material is disposed over each of the first plurality of acoustic wave resonators and has a height about the substrate that is smaller than a height of the layer of negative temperature coefficient of frequency dielectric material disposed over said one or more of the second plurality of acoustic wave resonators.
 15. The radio frequency module of claim 14 wherein the second layer of negative temperature coefficient of frequency dielectric material is a single continuous layer that covers the first plurality of acoustic wave resonators and the second plurality of acoustic wave resonators, the layer of negative temperature coefficient of frequency dielectric material being disposed over the second layer of negative temperature coefficient of frequency dielectric material.
 16. A wireless communication device comprising: an antenna; and a front end module including an acoustic wave filter configured to filter a radio frequency signal associated with the antenna, the acoustic wave filter including a substrate, a piezoelectric layer over the substrate, a first plurality of acoustic wave resonators disposed over the piezoelectric layer and arranged in series along a first branch, each of the first plurality of acoustic wave resonators including an interdigital transducer electrode interposed between a pair of reflectors, a second plurality of acoustic wave resonators disposed over the piezoelectric layer and arranged in parallel, each of the second plurality of acoustic wave resonators including an interdigital transducer electrode interposed between a pair of reflectors and being connected to the first branch and to ground, the interdigital transducer electrode of one or more of the second plurality of acoustic wave resonators having a wider duty factor than the interdigital transducer electrode of the first plurality of acoustic wave resonators.
 17. The wireless communication device of claim 16 wherein the first plurality of acoustic wave resonators and the second plurality of acoustic wave resonators are surface acoustic wave resonators.
 18. The wireless communication device of claim 16 wherein an additional layer is disposed between the substrate and the piezoelectric layer, the additional layer having a lower acoustic impedance than the substrate and configured to facilitate adhesion between the substrate and the piezoelectric layer.
 19. The wireless communication device of claim 16 wherein a layer of negative temperature coefficient of frequency dielectric material is disposed over one or more of the second plurality of acoustic wave resonators.
 20. The wireless communication device of claim 19 wherein a second layer of negative temperature coefficient of frequency dielectric material is disposed over each of the first plurality of acoustic wave resonators and has a height about the substrate that is smaller than a height of the layer of negative temperature coefficient of frequency dielectric material disposed over said one or more of the second plurality of acoustic wave resonators.
 21. The wireless communication device of claim 20 wherein the second layer of negative temperature coefficient of frequency dielectric material is a single continuous layer that covers the first plurality of acoustic wave resonators and the second plurality of acoustic wave resonators, the layer of negative temperature coefficient of frequency dielectric material being disposed over the second layer of negative temperature coefficient of frequency dielectric material. 